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Fix "unexpected null" handling overlapping file changes #1083

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Fix "unexpected null" handling overlapping file changes #1083

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73 changes: 44 additions & 29 deletions packages/metro-file-map/src/index.js
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Original file line number Diff line number Diff line change
Expand Up @@ -878,33 +878,39 @@ export default class FileMap extends EventEmitter {
const rootDir = this._options.rootDir;

let changeQueue: Promise<null | void> = Promise.resolve();
let eventsQueue: EventsQueue = [];
let eventStartTimestamp = null;
let nextEmit: ?{
eventsQueue: EventsQueue,
firstEventTimestamp: number,
firstEnqueuedTimestamp: number,
} = null;

const emitChange = () => {
if (eventsQueue.length) {
const hmrPerfLogger = this._options.perfLoggerFactory?.('HMR', {
key: this._getNextChangeID(),
if (nextEmit == null || nextEmit.eventsQueue.length === 0) {
// Nothing to emit
return;
}
const {eventsQueue, firstEventTimestamp, firstEnqueuedTimestamp} =
nextEmit;
const hmrPerfLogger = this._options.perfLoggerFactory?.('HMR', {
key: this._getNextChangeID(),
});
if (hmrPerfLogger != null) {
hmrPerfLogger.start({timestamp: firstEventTimestamp});
hmrPerfLogger.point('waitingForChangeInterval_start', {
timestamp: firstEnqueuedTimestamp,
});
if (hmrPerfLogger != null) {
hmrPerfLogger.start({timestamp: nullthrows(eventStartTimestamp)});
hmrPerfLogger.point('waitingForChangeInterval_start', {
timestamp: nullthrows(eventStartTimestamp),
});
hmrPerfLogger.point('waitingForChangeInterval_end');
hmrPerfLogger.annotate({
int: {eventsQueueLength: eventsQueue.length},
});
hmrPerfLogger.point('fileChange_start');
}
const changeEvent: ChangeEvent = {
logger: hmrPerfLogger,
eventsQueue,
};
this.emit('change', changeEvent);
eventsQueue = [];
eventStartTimestamp = null;
hmrPerfLogger.point('waitingForChangeInterval_end');
hmrPerfLogger.annotate({
int: {eventsQueueLength: eventsQueue.length},
});
hmrPerfLogger.point('fileChange_start');
}
const changeEvent: ChangeEvent = {
logger: hmrPerfLogger,
eventsQueue,
};
this.emit('change', changeEvent);
nextEmit = null;
};

const onChange = (
Expand Down Expand Up @@ -952,15 +958,14 @@ export default class FileMap extends EventEmitter {
return;
}

if (eventStartTimestamp == null) {
eventStartTimestamp = performance.timeOrigin + performance.now();
}
const onChangeStartTime = performance.timeOrigin + performance.now();

changeQueue = changeQueue
.then(async () => {
// If we get duplicate events for the same file, ignore them.
if (
eventsQueue.find(
nextEmit != null &&
nextEmit.eventsQueue.find(
event =>
event.type === type &&
event.filePath === absoluteFilePath &&
Expand All @@ -978,11 +983,21 @@ export default class FileMap extends EventEmitter {
const linkStats = fileSystem.linkStats(relativeFilePath);

const enqueueEvent = (metadata: ChangeEventMetadata) => {
eventsQueue.push({
const event = {
filePath: absoluteFilePath,
metadata,
type,
});
};
if (nextEmit == null) {
nextEmit = {
eventsQueue: [event],
firstEventTimestamp: onChangeStartTime,
firstEnqueuedTimestamp:
performance.timeOrigin + performance.now(),
};
} else {
nextEmit.eventsQueue.push(event);
}
return null;
};

Expand Down